[PATCH v3 5/9] board_f: Fix corruption of relocaddr

[Devarsh Thakkar]

Hi Simon, Tom,

On 15/08/23 04:13, Simon Glass wrote:
> Hi Devarsh, Nikhil, Tom,
> 
> On Wed, 9 Aug 2023 at 09:29, Bin Meng <bmeng.cn at gmail.com> wrote:
>>
>> On Thu, Aug 3, 2023 at 7:03 PM Bin Meng <bmeng.cn at gmail.com> wrote:
>>>
>>> On Thu, Aug 3, 2023 at 6:37 PM Bin Meng <bmeng.cn at gmail.com> wrote:
>>>>
>>>> On Tue, Aug 1, 2023 at 12:00 AM Simon Glass <sjg at chromium.org> wrote:
>>>>>
>>>>> When the video framebuffer comes from the bloblist, we should not change
>>>>> relocaddr to this address, since it interfers with the normal memory
>>>>
>>>> typo: interferes
>>>>
>>>>> allocation.
>>>>>
>>>>> This fixes a boot loop in qemu-x86_64
>>>>>
>>>>> Signed-off-by: Simon Glass <sjg at chromium.org>
>>>>> Fixes: 5bc610a7d9d ("common: board_f: Pass frame buffer info from SPL to u-boot")
>>>>> Suggested-by: Nikhil M Jain <n-jain1 at ti.com>
>>>>> ---
>>>>>
>>>>> Changes in v3:
>>>>> - Reword the Kconfig help as suggested
>>>>>
>>>>> Changes in v2:
>>>>> - Add a Kconfig as the suggested conditional did not work
>>>>>
>>>>>   common/board_f.c      | 3 ++-
>>>>>   drivers/video/Kconfig | 9 +++++++++
>>>>>   2 files changed, 11 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/common/board_f.c b/common/board_f.c
>>>>> index 7d2c380e91e..5173d0a0c2d 100644
>>>>> --- a/common/board_f.c
>>>>> +++ b/common/board_f.c
>>>>> @@ -419,7 +419,8 @@ static int reserve_video(void)
>>>>>                  if (!ho)
>>>>>                          return log_msg_ret("blf", -ENOENT);
>>>>>                  video_reserve_from_bloblist(ho);
>>>>> -               gd->relocaddr = ho->fb;
>>>>> +               if (IS_ENABLED(CONFIG_VIDEO_RESERVE_SPL))
>>>>> +                       gd->relocaddr = ho->fb;
>>>>>          } else if (CONFIG_IS_ENABLED(VIDEO)) {
>>>>>                  ulong addr;
>>>>>                  int ret;
>>>>> diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
>>>>> index b41dc60cec5..f2e56204d52 100644
>>>>> --- a/drivers/video/Kconfig
>>>>> +++ b/drivers/video/Kconfig
>>>>> @@ -1106,6 +1106,15 @@ config SPL_VIDEO_REMOVE
>>>>>            if this  option is enabled video driver will be removed at the end of
>>>>>            SPL stage, beforeloading the next stage.
>>>>>
>>>>> +config VIDEO_RESERVE_SPL
>>>>> +       bool
>>>>> +       help
>>>>> +         This adjusts reserve_video() to redirect memory reservation when it
>>>>> +         sees a video handoff blob (BLOBLISTT_U_BOOT_VIDEO). This avoids the
>>>>> +         memory used for framebuffer from being allocated by U-Boot proper,
>>>>> +         thus preventing any further memory reservations done by U-Boot proper
>>>>> +         from overwriting the framebuffer.
>>>>> +
>>>>>   if SPL_SPLASH_SCREEN
>>>>>
>>>>>   config SPL_SPLASH_SCREEN_ALIGN
>>>>
>>>> Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
>>>
>>> applied to u-boot-x86, thanks!
>>
>> Dropped this one from the x86 queue per the discussion.
> 
> I just wanted to come back to this discussion.
> 
> Do we have an agreed way forward? Who is waiting for who?
> 

I was waiting on feedback on 
https://lore.kernel.org/all/3b1e8005-f161-8058-13e7-3de2316aac34@ti.com/ 
but per my opinion, I would prefer to go with "Approach 2" with a 
Kconfig as it looks simpler to me. It would look something like below :

if (gd->relocaddr > (unsigned long)ho->fb) {
      ulong fb_reloc_gap = gd->relocaddr - gd->ho->fb;

      /* Relocate after framebuffer area if nearing too close to it */
      if (fb_reloc_gap < CONFIG_BLOBLIST_FB_RELOC_MIN_GAP)
             gd->relocaddr = ho->fb;
}

Regarding CONFIG_BLOBLIST_FB_RELOC_MIN_GAP
-> This describes minimum gap to keep between framebuffer address and 
relocation address to avoid overlap when framebuffer address used by 
blob is below the current relocation address

-> It would be selected as default when CONFIG_BLOBLIST is selected with 
  default value set to 100Mb

-> SoC specific Vendors can override this in their defconfigs to a 
custom value if they feel 100Mb is not enough

Also probably we can have some debug/error prints in the code to show 
overlap happened (or is going happen) so that users can fine tune this 
Kconfig if they got it wrong at first place.

I can re-spin updated patch if we are aligned on this,
Kindly let me know your opinion.

Regards
Devarsh

> Regards,
> Simon